This application is based on, and claims priority to, Japanese application number Heisei 10-126268, filed on May 8, 1998, in Japan, and which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical communication system which compensates for dispersion. More specifically, the present invention relates to an optical communication system having a transmission path with sections which overcompensate for dispersion occurring in the sections, so that the total dispersion at a point downstream of the sections is approximately zero.
2. Description of the Related Art
In ocean transversal long-haul optical communication systems covering distances of several thousands kilometers, signal transmission is conducted using optical regenerating repeaters which convert an optical signal to an electrical signal to perform retiming, reshaping and regenerating.
However, optical amplifiers which can directly amplify light, without converting the light into an electrical signal, are being investigated for use in optical communication systems. The use of such optical amplifiers can greatly reduce the number of parts in a repeater, improve reliability, and drastically reduce cost, as compared to the use of conventional optical regenerating repeaters.
Moreover, wavelength division multiplexing (WDM) is being used in optical communication systems in increase transmission capacity. With WDM, two or more optical signals at different wavelengths are multiplexed together into a WDM signal. The WDM signal is then transmitted through a single optical fiber as a transmission line. WDM can be compared to a conventional optical communication system where only one optical signal is transmitted through the optical fiber.
An optical amplifier, which directly amplifies light without converting the light into an electrical signal, can be used to amplify a WDM signal. In this case, the optical amplifier will simultaneously amplify each optical signal in the WDM signal.
Therefore, an optical communication system which uses WDM in combination with optical amplifiers can provide high capacity, long-haul optical transmission with a relatively simple, economical structure. Unfortunately, an optical signal transmitted through such an optical communication system can experience a large amount of distortion.
Accordingly, it is an object of the present invention to provide an optical communication which appropriately compensates for dispersion for optical signals transmitted through the system.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing objects of the present invention are achieved by providing an optical communication system which includes a transmission path through which a light is transmitted to a specific point, such as to a receiver. The transmission path includes a plurality of sections so that the light travels through the sections to the specific point. Each section overcompensates for dispersion produced in the respective section for the light so that an amount of dispersion for the light at the specific point is substantially zero.
Objects of the present invention are also achieved by providing an optical communication system which includes a transmission path having a plurality of sections so that the light travels through the sections to a specific point. Each section overcompensates for dispersion produced in the respective section for the light to control the amount of dispersion for the light at the specific point.
Objects of the present invention are further achieved by providing an optical communication system which includes a transmission path. Light is transmitted through the transmission path to a specific point. The transmission path includes a plurality of sections so that the light travels through the sections to the specific point. Each section overcompensates for dispersion produced in the respective section for the light to reduce the total amount of dispersion for the light at the specific point.
Objects of the present invention are also achieved by providing a transmission path including a plurality of sections through which light travels to a specific point, wherein the plurality of sections together overcompensate for dispersion produced in the sections for the light. The total amount of overcompensation in the sections taken together is substantially equal to a residual dispersion in the light at the specific point which would occur if the dispersion for the light in each section was approximately zero.
Further, objects of the present invention are achieved by providing an optical communication system including a transmission path through which a light is transmitted to a specific point, where m dispersion compensators are positioned along the transmission path to divide the transmission path into (m+1) blocks. Each dispersion compensator overcompensates for dispersion produced in the preceding block so that the amount of dispersion for the light at the specific point is substantially zero.
In addition, objects of the present invention are achieved by providing an optical communication system which includes a transmission path through which a light is transmitted to a specific point. A dispersion compensator is positioned along the transmission path before the specific point and overcompensates for dispersion provided by the transmission path to the light up to a point along the transmission path before the specific point, so that the amount of dispersion for the light at the specific point is controlled, reduced, or is substantially zero.